Strange thumping feeling in 2001 ST

[Stephen Antonucci]

Good evening all !



I have a 2001 4x4 ST and I have been experiencing a strange problem for about a year now.



When I brake somewhat harder than normal and come to a complete stop, I often feel a

slight thump, or shift, or unloading phenomenon once I let off the brake petal. You don't

hear any noise, but rather feel it. I have had my ST to my Ford dealer twice for this. Once,

they claimed it was the sway bar bushings. They were replaced and the problem seemed to

be fixed. Unfortunately, that only lasted for about one month. Then, the problem came back.

I took it back and they went all over the truck ( so they claim ) and they couldn't find anything

out of the norm. If I didn't know better, I would swear that the the suspension is shifting

somehow. This seems to be more prevalent while stopping on declines.



I also thought that possibly the brakes were somehow causing this. Again, I mentioned this

to my dealer and they came back with nothing.:wacko::wacko::wacko:



Have any members ever experienced anything like this?



Steve

 

[Gavin Allan]

Lube the driveshaft slip joint.

 

[shawn stonbraker 2]

Check shock mount bushings.(especially the bottom) Sometimes they go bad and go AWOL and then the shock is able to "flex" inside the mount causing a "thump". Does it only do it right after you take your foot off the brake and not during the brake cycle?

 

[Stephen Antonucci]

Hi Gavin,



Can you please be a little more specific for me here? What exactly is the driveshaft

slip joint? Is this a sort-of telescoping driveshaft mechanism of sorts? Guess I will

have to inform my Ford dealer of this so I want to sound a little more knowledgeable.



Thanks,

Steve

 

[Stephen Antonucci]

Hi Stonemiser,



To the best of my recollection, it always seems to do this as soon as I let off the brake.

It may happen sometimes once I start to accelerate. One sort of goes with the other,

you know!



Steve

 

[Allen Brandt]

Sticky brakes perhaps?

 

[shawn stonbraker 2]

Sticky brakes is one, but if it is happening when you leave off and hit the gas, it could be a universal joint in the driveshaft. The sticky brakes part is when you leave off the brakes the wheels turn alittle causing the brakes to break free of the rotors causing a "thump". man, I know, it could be alot of things but with the situation you described, could be brakes, suspention, or drivetrain. There, pretty much "bumper to bumper". (my attempt at light humor, sorry)

 

[Stephen Antonucci]

Bumper-to-bumper you say - huh?:blink:



That's pretty much what the dealer's service dept. has been doing...... going from the front

bumper to the rear bumper looking for something..... anything......

 

[shawn stonbraker 2]

Really does sound like sticky brake pads or your caliper guides.

 

[Jim Dolinski]

Take a look at the rear shocks, sounds like you might have one or both going bad

 

[Gavin Allan]

Driveshaft slip joint is where the driveshaft goes into the transmission (I think. I can't remember what the underneath of the Trac looks like!). Basically, they have to drop the driveshaft, clean the splines, coat with new grease, and put it all back togther. Shouldn't take much more than a 1/2 hour labor at a shop. The "thump" is the noise of the driveshaft slipping in and out--because it needs lube, it is sticking and doesn't slide easily until it loads up with enough force to overcome the stickyness.

 

[Dre L]

I've had this condition since new (2001 J2). I think it has more to do with causing the suspension to bob up and down hard.



It happens when you brake moderately hard (stopping for a light), then at the last second before you stop, you let up on the brake so you don't stop so hard.

 

[Gavin Allan]

Yeah, it is the driveshaft length change due to the suspension movements. Grease that sliplink!